Abstract: Confirmed, "Zero Attach" properties of Finar Buffer between copper leadframe and FB using solder.
Finar Buffer as you can see in the drawing below is a self-standing closely packed pin grid array (CPPGA).
When attach material is put between Finar Buffer and another material it is forced into the interstitial spaces between the pins, or seen another way the pins pierce the attach material, such that between the end of the pin and the facing material there is "Zero Attach".
Fantastic grip! BUT more importantly it minimizes the thermal resistance of the attach material!!